Offsite construction is the future – ignore it at your peril

Offsite construction is on the rise again, driven by the demand for homes, skills shortages in the building industry and environmental considerations. Levitt Bernstein’s Zohra Chiheb looks at the opportunities – and challenges – that its growth presents for architects.

Over the last 100 years, housing production has seen offsite manufacturing come and go in many guises, from concrete sandwich panels, to steel truss boxes, to double plastic shells. A system is developed that appears to provide cheaper housing production; then there is some sort of failure, actual or perceived – such as damp and fire safety issues highlighted in a notorious 1983 World in Action TV documentary, which caused the timber-frame housing market to crash – and the system is discredited.

Following the gas explosion at Ronan Point in 1968, requirements for structural performance were tightened. Yet even today many lenders refuse to provide finance for schemes using the offsite large panel system used on that tower block – technology seen as revolutionary in the 60s.

More recently, prefabricated buildings have been plagued by damp and water ingress because details were not properly co-ordinated across the project team. In response, warranty providers such as the NHBC have updated their requirements.

There are still problems. Last year, developer Forest City Ratner, having completed the world’s tallest modular building at 461 Dean Street in New York, sold its offsite factory. The project had been completed two and a half years late, plagued by disputes between contracting partners. However, one of the former directors, Roger Krulak, has since bought the factory and technology, maintaining that offsite is the future and that the problems experienced at Dean Street can be resolved.

So have we learnt the lessons of these past set-backs? Indeed, are we at the start of another prefabrication renaissance? Housing today is providing a number of particular challenges, and offsite technology is developing to tackle each one:

· There is a substantial housing shortage in parts of the UK. The Greater London Authority has stated that 50,000 new homes a year are needed in London to keep pace with demand. In some areas this means housing is being proposed at densities previously unseen in this country.

· An ageing population means we need different types of homes, ones that are flexible enough to accommodate future changes.

· The rise of student housing and the build-to-rent model has seen the growing emergence of ‘contractor-developer’ clients, who require improved durability and low maintenance costs.

· The lack of skilled workers is pushing costs up for traditional construction methods, a challenge set to intensify if Britain restricts future immigration after leaving the EU.

Offsite technology is responding to all these challenges. Steel frame volumetric systems are being used to build to high densities very quickly. In the Wembley Regeneration Area in north-west London, HTA Design, with Tide Construction and Vision Modular Systems, has just completed Apex House. This 29-storey student accommodation block took just 12 months to construct. It is currently the tallest modular building in Europe – though HTA and Tide will top their own record if a 44-storey modular build-to-rent apartment building in Croydon goes ahead.

Swan Housing is producing cross-laminated timber (CLT) homes at its factory in Basildon, working with Pollard Thomas Edwards and CF Møller, with a focus on making the design flexible enough so homes can be adapted in the future as residents’ needs change.

In Manchester, Salford and North Shields, offsite technology is allowing home-buyers to be involved in designing the layout of their homes. Flexible floorplans produced by ShedKM for hoUSe by Urban Splash allow ‘mass customisation’, and the same outer module is being used to create many different types of home.

Legal & General has spent millions developing a volumetric CLT factory outside Leeds, where it intends that its factory-fitted finishes will be of higher quality than traditional methods, reducing the need for ‘lower-skilled’ workers on building sites. My practice, Levitt Bernstein, is looking at offsite technologies as part of several estate regeneration projects. The lightweight structure and fast installation times that can be achieved with offsite make it a good option for rooftop extensions as part of the regeneration of 1950s and ’60s housing estates, adding homes without the need to decant existing residents.

For architects, as champions of design and placemaking, the rise of offsite presents both opportunities and constraints. Offsite should be a tool to help us build better, rather than being the main driver of design. The focus needs to be on the people who will live in the homes we design. Buildings need to interface well with their landscape. Overly repetitive modules, driven by offsite system requirements, can create bland, inappropriate buildings. Worryingly, some players in the offsite market intend to roll out standard house types for deployment across the country, with no architectural involvement or site-specific design consideration.

On the other hand, the specialist knowledge required for offsite manufacturing can mean that architects are more likely to be retained throughout RIBA stages, with greater control over design and quality. Perhaps in the future more architects will have in-house offsite teams? Or perhaps developer-manufacturers will have in-house architects? Much of the change is being driven by the understanding that offsite technology can achieve lower build costs, but how can we learn from past mistakes, and harness offsite practices to produce higher-quality, long-life buildings that perform better environmentally and meet residents’ future needs? What can we learn from the advanced robotic technology used in the car industry to push finishing techniques beyond someone hand-painting architraves in a shed?

The forward-looking nature of the offsite industry will lead to greater automation, and architects need to thoroughly engage with this. There will be different types of jobs requiring different skills. Safety in the building industry could be greatly improved by moving production to a controlled environment, which could in turn attract more people to the industry.

Many more companies are coming into the offsite market with various systems, and new factories are being built. This is both exciting and risky. If there is a downturn in the market, smaller players could fold. The Construction Leadership Council has recommended factory-sharing to spread the risk for small and medium enterprises looking to use offsite solutions.

Offsite technology could also be a fantastic opportunity to reduce the construction industry’s carbon footprint. Factory-produced elements result in less waste, as offcuts from processes can often be reused or recycled at the factory. Fewer trades means fewer vehicle trips to site. Timber products used in systems such as CLT act as a carbon sink, further reducing greenhouse gas emissions.

The Grenfell Tower disaster has taught us that new systems need to be tested as a whole, and façade systems need to be considered alongside building layout. It is crucial that regulation keeps pace with emerging technology, and the government needs to keep ahead on the performance required from these systems. Australia changed its building code last year in response to the growing number of medium-rise CLT buildings. It now requires sprinklers in buildings and timber to be either thick enough to self-protect, or to be clad in fire-rated plasterboard.

Systems need to be tested and certified to a standard that protects future homeowners. A report last year by the Building Societies Association found that high street lenders are better able to understand and provide mortgages on systems that have been subjected to some form of widely accepted accreditation, for example the Build Offsite Property Assurance Scheme (BOPAS).

The government has recognised the importance of the offsite industry through the Farmer Review, which looked at tackling construction skills shortages. It could encourage offsite through a build-to-rent programme or by directly funding offsite construction projects. The GLA’s report, Designed, Sealed, Delivered: The Contribution of Offsite Manufactured Homes to Solving London’s Housing Crisis, published this year, has urged London’s mayor to look at the potential of using TfL-owned land to stimulate the sector.

Academic research will also help inform industry change. Universities are producing research that explores the benefits of the different technologies, and identifies where there are gaps in our knowledge. A report, due to be published in November and led by the University of the West of England for a consortium of seven housing associations, has found that there is a real need for post-occupancy evaluation to establish how well offsite manufacturing is meeting residents’ needs.

Designers need to embrace this change to make sure offsite technology is working for us and not the other way around. We can do this by keeping abreast of new developments and working closely with the manufacturing industry. Early procurement, and joined-up working throughout the design process, enhanced by the use of BIM software, should allow design and fabrication to work in harmony, and create architecture informed by, but not driven by, the system.